First thing to try, and I speak from experience, is to put Thetford Drain Valve Lubricant in your tank. Our valve was stuck open which is the opposite of yours. It's better and recommended to treat the valve with it closed. So at the advice of the local RV supply and shop, we bought the Thetford, ran hot water in our toilet (using buckets), managed to get the valve closed, which is what you want. We let it sit (preferred to drive around so the liquid swishes around), but for us it worked. We can open and close easily now. I put additional treatment in along with two gallons of hot water. Why they stick can be because sludge builds up around it much like the valve on your lawn mower when you move between mulch and bag. Try that first before you panic and have to take things apart.
2011 Bighorn 3055RL
2011 F350 DRW 6.7L 4x4 Diesel Lariat and Hensley TrailerSaver BD3
1992 Jeep ZJ and 1978 Coleman Concord Pop-Up for remote camping
Dave & Renee plus (Champ, Molly, Paris, Missy, and Maggie in spirit), Mica and Mabel, both Rat Terriers!
